Apparatus for automatic control of product fill dimension

ABSTRACT

Apparatus for automatic control of the fill dimension of a product formed in a rolling mill by sensing the fill dimension of the finished product and comparing this value to a predetermined reference value to form a resultant error signal. This resultant error signal modifies the height of loops between successive stands of the mill to vary the product fill dimension. The apparatus includes provision for increasing the gain if successive errors of fill dimension in the same direction are sensed and for decreasing the gain if successive errors in the opposite directions are sensed.

United States Patent [191 Dornbusch et a].

[4 Oct. 9, 1973 APPARATUS FOR AUTOMATIC CONTROL 3,526,113 9/1970Mclslaughen 72/8 ()1? P O U FILL DIMENSION 3,650,135 3/1972 Skelton etal 72/8 [75] Inventors: Paul E. Dornbusch; Thomas D. Prima ryExammer-Mrlton S. Mehr Johnson both of Roanoke Att0rneyArn0ld E. Renneret al. [73] Assignee: General Electric Company, Salem,

' Va. [57] ABSTRACT [22] Filed: June 30, 1972 Apparatus for automaticcontrol of the fill dimension of a product formed in a rolling mill bysensing the fill [2]] Appl' 268085 dimension of the finished product andcomparing this value to a predetermined reference value to form a re-[52] U5. Cl. 72/9, 72/16 sultant r r ign l- This re ltan e r r ign lmodi- [51] Int. Cl B21b 37/12 ties e igh of lo p w n c sive s nd of [58]Field of Search 72/8, 9, 10, 11, the mill t vary the product filldimension. The appa- 72/12, 16 ratus includes provision for increasingthe gain if successive errors of fill dimension in the same direction 56] References Cited are sensed and for decreasing the gain if successiveer- UNITED STATES PATENTS rors in the opposite directions are sensed.3.251.207 5/l966 Wilson 72/12 .7 Claims, 4 Drawing Figures 26 27 LOOPLOOP LOOP LOOP MOTOR SENSO MOTOR SENSOR MOTOR SENSOR MOTOR SENSOR MOTOR3| I l l L OP SPEED L P P ED P SPEED LOOP SPEED REG. REG. RES. E RESREG. RESv A 37 MAX. 3940 MIN.

| REFERENCE I BUZZER GATE 7 LOOP HEIGHT 7 LIMIT ERROR PATENTEDUET 9%3,763,678

SHEET 10F 3 iii) FIG. 1

NOISNEHIO UHGTDQHS PATENIED DDT 91873 SHEET 30F 3 LET HEAD HAS CHEDSENSOR YES BILLET TAIL HAS YES REACHED STAND 22 UNDER FILL 59 TOGGLE SETT No 6| DECREASE GAIN I SET OVERFILL TOGGLE RESET UNDERFILL TOGGLE YESUNDERFILL YES TOGGLE sET 48 OVERFILL TOGGLE sET DECREASE INCREASE GAIN T/50 MULTIPLY ERROR BY GAIN SET UNDERFILL RESET OVERFILL I sum WITHHEIGHT RE LOOP FERENCE TOGGLE TOGGLE APPARATUS FOR AUTOMATIC CONTROL OFPRODUCT FILL DIMENSION BACKGROUND OF THE INVENTION .changes to obtainthe desired tension regulation throughout the mill speed range. This wasgenerally accomplished by providing interstand tension sensing devices,such as a loop height sensor betweenadjacent stands in the mill, andusing a signal from the sensor to vary the speed of the rolls which hasthe effect of varying the tension in the product.

In attempts to keep a constant product dimension, the ratio of the standspeed to mass flow is generally the controlling factor. Although thestand speed is relatively insensitive to variations and easy to control,the mass flow is relatively sensitive to product parameters andtherefore is relatively difficult to control. The difficulty ofcontrolling mass flow in the prior art limited the ability to maintainproduct dimensions.

Many modern, high production mills for forming rods, bars, etc., utilizea plurality of stands in a finishing train and have regulated loopsbetween successive stands. The difficult problem of controlling the massflow of a product in such mills has been substantially overcome by thepractice of this invention. This is accomplished by sensing immediatelyafter the final finishing stand the product fill dimension and comparingthis dimension to a predetermined reference value. Any deviation fromthe desired fill dimension on the finished product forms an error signaland automatically modifies the loop heights as a function of thedimension deviation or error signal. The loop heights are regulated bychanging the speed of a plurality of preceding stands.

SUMMARY OF THE INVENTION lt is therefore an object of this invention toprovide an improvedautomatic control of the fill dimension of a product.

It is another object of this invention to provide an automatic controlof mass flow to control the fill dimension of a product.

It is a further object of this invention to provide an improvedautomatic control of the fill dimension of a product by regulation ofthe speed of a plurality of preceding stands.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 2 is a simplified diagram of aportion of a mill train showing a regulated loop between two stands ofthe finishing train.

FIG. 3 is a simplified diagram of an automatic fill control forcontrolling the fill dimension in accordance with this invention.

FIG. 4 is a simplified logic flow chart further illustrating theoperation of the automatic fill control.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1 of thedrawings, there are illustrated three sectional views of a product,specifically in the form of a rod 11, after it leaves the last finishingstand and shaping has been accomplished. Two dimensions are indicated inFIG. 1, a shoulder dimension and a fill dimension. The shoulderdimension is the dimension perpendicular to the rolls of the aforesaidstand. The fill dimension is the dimension parallel with the rolls ofthe stand.

The shoulder dimension is usually determined primarily by the rollgrooves and screw settings of the stands. It is relatively insensitiveto variations in incoming product parameters and stand speeds;therefore, it is relatively easy to control. The fill dimension iscontrolled primarily by the ratio of stand speed to mass flow; it issensitive to product parameters and relatively difficult to control.

Assuming that the mill is properly set up and running a good product, asatisfactory rod section will develop, as shown at llla in FIG. 1. Therod 11b in FIG. 1 shows the cross section of a finished product in anunderfilled state, forming flats in the fill dimension. The rod in FIG.1 shows the cross section of a finished product in an overfilled state,forming fins in the fill dimension.

Inspection of the geometry of the sections in FIG. 1 reveals that therelationships between the cross section area and the fill dimension isnon-linear. This fact, in addition to other non-linearities in theprocess (such as roll spacing), results in wide variations in therelationships between mass flow and fill dimension.

FIG. 2 is illustrative of a portion of a modern, high production millhaving a regulated loop between two stands of the finishing train. FIG.2 illustrates a product in the form of a rod 12 moving in the directionindicated by arrow 13 and driven by horizontal stand 14 and verticalstand 15. Hold down rolls l6 and 17 keep the product 12 in contact withloop thrower 18 and the height of the formed loop is sensed at thecenter line 19 of the loop formed by the loop thrower.

FIG. 3 shows the product 12 advancing in the direction of arrow 20 anddriven by vertical stands 21, 23, and 25 and horizontal stands 22 and24. Between each horizontal and vertical stand, such as stands 22 and 23is a loop, corresponding to the loop shown in FIG. 2, the height ofwhich is sensed by loop sensor 26. The motor 27 of stand 23 is regulatedthrough a speed regulator 28 by a loop regulator 29 which compares aninput from the loop sensor 26 with an input from an amplifier 30. Theoutput of the loop regulator 29 is supplied to the speed regulator 28for controlling the speed of the motor 27, and thereby controlling theloop height. Each of the stands 22, 24, and 25 is also provided with acorresponding loop sensor, motor, speed regulator, and loop regulator.The loop regulator of each stand is connected to the amplifier 30.

In order to control automatically the plurality of stands forming thefinishing train, the control circuit shown at the bottom portion of FIG.3 is employed. After the product 12 travels through the final stand 25,the fill dimension of the product 12 is sensed by a sensor 31, which maybe in the form of an infrared micrometer, located immediately after thefinal stand. sensor 31 produces a fill dimension error signal which isintergrated in calculator 32 for a fixed time. The calculator 32 alsoreceives a signal from a loop height reference 33. The loop heightreference is the loop height value against which the actual loop heightsensed by loop sensor 26 is compared in the loop regulator 29. Thesignal from the loop height reference 33 is summed in the calculatorwith the error signal. The resultant signal is supplied through a gate34 to the loop height reference and incrementally varies the loop heightreference in proportion to the error signal. This proportion isautomatically calculated to compensate for variations (non-linearities)in the relationships between mass flow and fill dimension. The loopheight reference, which is varied as indicated, establishes a loopheight which, if maintained and with conditions remaining unchanged,would result in a correct fill dimension. The loop height referencesignal is supplied to the calculator, it is summed with the loop heightreference to establish a new value for the loop height reference.

In addition to the automatic control signal from calculator 32 to gate34, a manual input is also provided to gate 34. This manual input may beutilized if the sensor 31 is temporarily disabled or if, for any reason,it is desired to override the automatic control.

The output of the loop height reference is connected throughdigital-to-analog converter 37 to the amplifier 30 to provide a signalto the loop regulator for controlling the speed of stand 23 and therebythe loop height of the product between stands 22 and 23. It will benoted from FIG. 3 that the signal from the amplifier 30 is connected notonly to the loop regulator 29 of stand 23 but also to corresponding loopregulators associated with stands 22, 24, and 25. Hence, all four loopsare simultaneously adjusted, thereby quadrupling the change in filldimension which can be achieved by adjusting a single loop.

Loop height reference 33 is also connected to a loop height limit device38 which is equipped with maximum limit light 39, a minimum limit light40 and a buzzer 41 to indiciate that the maximum or minimum setting ofthe loop height which can be controlled by the automatic fill controlhas been reached. Each of the loops may be automatically controlled bythe control system of this invention so long as the loop height remainswithin a predetermined range corresponding to the maximum and minimumlimits. If the loop height goes beyond this range, the appropriate lightsignals the operator to make appropriate adjustment of roll screws tobring the loop height into the range for automatic control.

The operation of the automatic control of this invention can be moreclearly understood by reference to the further details of operationshown in the logic flow chart of FIG. 4. When a sensor, represented bylogic unit 42, senses the head of the product, at stand 25, operation ofthe automatic control is initiated provided the tail of the product hasnot yet reached stand 22, as indicated by logic unit 43. If the abovetwo conditions are met, fill sensor logic unit 44, corresponding toinfrared micrometer 31 in FIG. 3, supplies an error signal to thecalculator 32 in FIG. 3 where the fill dimension error signal isintegrated over a fixed period of time. In the logic flow chart of FIG.4, the elements included in the dashed block 32a indicate the functionsperformed in the calculator 32 shown in FIG. 3.

When the sensing function indicated by logic unit 44 is completed, thecalculator 32 shown in FIG. 3 will have integrated the error signal overa period of time corresponding to the travel of a given length ofproduct past the sensing point, and the resultant signal will beproportional to the average error in that length of product. Completionof the sensing function by logic unit 44 initiates error sensing logicin the logic unit 45. If no error exceeding the error preset in logicunit 45 is indicated, the error sensing logic unit 45 will restart thetotal logic system through a logic unit 46 incorporating overfill andunderfill toggles (flip flops in an electronic system). In the flowchart, logic unit 46 is identified as resetting overfill and underfilltoggles. It will be understood that this language indicates that underthis condition the toggles (flip flops) are placed in their originalcondition, that is, not set.

Anytime an underfill greater than the error preset in logic unit 45 issensed, the sequence of events is illustrated on the underfill (rightside) of the logic flow chart. If this condition occurs, and neither theunderfill toggle nor the overfill toggle is set at the time, asdetermined by logic units 47 and 48 respectively, the logic unit 49 setsthe underfill toggle and resets the overfill toggle, that is, places theoverfill toggle in its original (non-set) state.

In the preferred embodiment of this invention, a single toggle or flipflop comprises both the logic units 48 and 55 identified as overfilltoggles in FIG. 4 and a single toggle or flip flop comprises both thelogic units 47 and 56 identified as underfill toggles in FIG. 4. Itwill, therefore, be understood that the setting or resetting of logicunits 47 and 48 shown on the right, or underfill, side of the flow chartin FIG. 4 results in the setting or resetting of the correspondingoverfill and underfill toggles of logic units 56 and 55 shown on theleft, or overfill, side of the flow chart. Thus the setting of thetoggle by any logic unit, such as logic unit 47, will perform anidentical function in the other corresponding logic unit 56 in logicflow chart of FIG. 4.

Logic unit 49 is connected to a logic unit 50 where the error signal ismultiplied by the gain. This multiplied signal is summed with a signalfrom the loop height reference 33 (FIG. 3) in logic unit 51 (FIG. 4) toproduce a new and lower loop height reference. The new loop heightreference causes all four loops as depicted in FIG. 3 to decrease inheight. This results in an increased fill dimension after a transienttime sufficient to permit the loops to reach a steady state condition atthe new height plus the time required for the product to travel from thestand 22 to the sensor 31.

After a correction, operation of the sensing logic unit 44 (i.e., sensor31 in FIG. 3) will not be initiated again until after the aforementionedtransient time plus the aforementioned product travel time, as indicatedby the logic unit 54.

In a similar manner, anytime an overfill greater than the error presetin logic unit 45 is sensed, the sequence of events is illustrated on theoverfill (left side) of the logic flow chart. If this condition occurs,the loop height reference will be increased. This causes all four loopsto be increased in height, resulting in decreased fill dimension. Thisis accomplished by connecting the logic unit 45 to overfill logic unit55 which in turn is connected to logic unit 50 through the seriallyconnected underfill logic unit 56 andlogic unit 57. Logic unit 57 setsthe overfill toggle and resets the underfill toggle, that is, places theunderfill toggle in its original (non-set) state. This affects the stateof logic units 55 and 56 and also the state of logic units 47 and 48.

After a correction, reading by the fill sensor indicated by the logicunit 44 will not be initiated again until after transient timesufficient to permit the loops to reach a steady state condition at thenew height, plus the time it takes the product to travel from stand 22to the sensor.

If two consecutive underfill or two consecutive overfill errors greaterthan the preset error of logic unit 45 are detected, the gain willautomatically change by an amount calculated to minimize the error afterthe second correction. With two consecutive underfill errors, this isaccomplished on the underfill portion of the logic flow chart. Logicunit 47 is set by the first sensing of an underfill error exceeding thepreset error; when the second underfill error is sensed, logic unit 47is then connected to logic unit 49 through increase gain logic unit 58.Logic unit 58 causes the gain multiplied in logic unit 50 to increase byan amount calculated to reduce the error to zero.

Likewise, with two consecutive overfill errors, the gain is changed asillustrated on the overfill portion of the logic flow chart. Logic unit55, which is set by the first sensing of an overfill error exceeding thepreset error, is connected to logic unit 57 through increase gain logicunit 59. Logic unit 59 then causes the gain multiplied in logic unit 50to increase by an amount calculated to reduce the error to zero.

When an overfill is followed by an underfill, the operation isillustrated as follows. Since there was no preceding sensing ofanunderfill error, the underfill logic unit 47 is not set. Since there hasbeen a preceding sensing of overfill error, however, logic unit 48 hasbeen set. Under these conditions logic unit 48 is connected to logicunit 49 through decrease gain logic unit 60. This decreases the gain byan amount calculated to reduce the error to zero.

When an underfill is followed by an overfill, the sequence of operationis illustrated on the overfill portion of the logic flow chart. Sinceoverfill logic unit 55 is not set and underfill logic unit 56 is set,logic unit 56 is connected to logic unit 57 through decrease gain logicunit 61. This decreases the gain by an amount calculated to reduce theerror to zero.

To relate the significance of gain as discussed above in connection withthe flow chart of FIG. 4 to the physical arrangement of the mill asshown in FIG. 3, it is observed that gain in the automatic controlsystem of FIG. 3 refers to the magnitude of loop height change initiatedby a given increment of measured fill error. The effect of a change inloop height on the fill dimension is not constant, differing, forexample, dependent upon whether overfill or underfill is involved andfurther involving a non-linear relationship. The system illustrated inFIG. 4 adapts to varying conditions by modifying the system gain whensuccessive samples show error in the same direction, indicatingundercorrection, or in opposite directions, indicating overcorrection.

In operation an operator would provide coarse control of the filldimension by manually adjusting the speed and/or screws on the precedingstands until the fill dimension is in the range of the automatic fillcontrol.

If the sensor 31 senses an oversized fill dimension, it will apply ahigher loop height reference. The resulting higher loops cause higherpull back force (back tension) on the product 12. The higher backtension reduces the mass flow, thus reducing the product fill. Thereduced mass flow in the delivery stand would cause the loop height toincrease beyond the new loop height reference; however, the loop sensorsenses loop height above the new reference and automatically increasesthe speed of the delivery stand to maintain the loop at the new height.The higher stand speed increases the mass flow to maintain the mass flowat a constant valve. The net effect is as follows:

1. Higher loop height 2. Increased back tension 3. Higher deliveryproduct linear speed 4. Constant mass flow 5. Reduced product filldimension.

In one embodiment of this invention the variation in one loop results infill dimension variations of between 5 to 10 mils in diameter.Therefore, in order to automatically control the fill dimension of aproduct in a range of at least 20 to 40 mils in diameter, an automaticcontrol system involving four loops, as illustrated in FIG. 4 isemployed.

While a specific embodiment of this invention has been shown anddescribed, it will be apparent to those skilled in the art thatmodifications are possible without departing from the inventive conceptsherein described. It is intended, therefore, to cover by the appendedclaims all modifications falling within the spirit and scope of thisinvention.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. Apparatus for the automatic control of the fill dimension of aproduct formed in a rolling mill, said apparatus comprising: v

a. a plurality of stands for performing a work function on the product;

b. sensing means for sensing the fill dimension of the product aftercompletion of the work function on the product;

c. comparator means for comparing the fill dimension with apredetermined reference value to form a resultant error signal; and

d. modifying means for automatically modifying the speed of theplurality of stands as a function of said error signal to control theproduct fill dimension.

2. Apparatus as recited in claim 1 wherein the means for modifying thespeed of the plurality of stands includes means for automaticallydeveloping a signal so proportioned to said error signal as tocompensate for non-linearities in the relationship between mass flow ofthe product and the product fill dimension.

3. Apparatus as in claim 1 wherein said sensing means is an infraredmicrometer.

4. Apparatus for the automatic control of the fill dimension of aproduct formed in a rolling mill, said apparatus comprising:

a. a plurality of stands for performing a work function on the product;

b. each of said stands including a means for forming loops in theproduct during the performing of a work function on the product;

c. sensing means for sensing the fill dimension of the product aftercompletion of the work function on the product;

d. comparator means for comparing the fill dimension with apredetermined reference value to form a resultant error signal; and

e. modifying means for automatically modifying the height of theplurality of loops as a function of said error signal to control theproduct fill dimension.

5. Apparatus in claim 4 wherein the means for modifying the height ofthe loops includes means for automatically developing a signal soproportioned to said error signal as to compensate for non-linearitiesin the relationship between mass flow of the product and the productfill dimension.

6. Apparatus for automatic control of the fill dimension of a productformed in a rolling mill, said apparatus comprising:

a. a plurality of stands for performing a work function on the product;p b. means for forming a loop in the product between successive stands,each loop having a height within a predetermined range;

c. sensing means for sensing the fill dimension of the product aftercompletion of the work function on the product;

d. comparator means for comparing the fill dimension with apredetermined reference value to form a resulting error signal; and

e. means for receiving said error signal and transmitting an outputsignal to effect a change in the height of said loops dependent uponsaid error signal;

f. said last-named means including means for modifying said outputsignal to increase the magnitude thereof when said sensing meansindicates two successive fill errors in the same direction and todecrease the magnitude thereof when said sensing means indicatessuccessive fill errors in opposite directions.

7. Apparatus as recited in claim 6 wherein said means for receiving saiderror signal includes means for multiplying said error signal by avariable gain, and wherein said gain is increased when said sensingmeans indicates two successive fill errors in the same direction andsaid gain is decreased when said sensing means indicates successive fillerrors in opposite directions.

1. Apparatus for the automatic control of the fill dimension of aproduct formed in a rolling mill, said apparatus comprising: a. aplurality of stands for performing a work function on the product; b.sensing means for sensing the fill dimension of the product aftercompletion of the work function on the product; c. comparator means forcomparing the fill dimension with a predetermined reference value toform a resultant error signal; and d. modifying means for automaticallymodifying the speed of the plurality of stands as a function of saiderror signal to control the product fill dimension.
 2. Apparatus asrecited in claim 1 wherein the means for modifying the speed of theplurality of stands includes means for automatically developing a signalso proportioned to said error signal as to compensate fornon-linearities in the relationship between mass flow of the product andthe product fill dimension.
 3. Apparatus as in claim 1 wherein saidsensing means is an infrared micrometer.
 4. Apparatus for the automaticcontrol of the fill dimension of a product formed in a rolling mill,said apparatus comprising: a. a plurality of stands for performing awork function on the product; b. each of said stands including a meansfor forming loops in the product during the performing of a workfunction on the product; c. sensing means for sensing the fill dimensionof the product after completion of the work function on the product; d.comparator means for comparing the fill dimension with a predeterminedreference value to form a resultant error signal; and e. modifying meansfor automatically modifying the height of the plurality of loops as afunction of said error signal to control the product fill dimension. 5.Apparatus in claim 4 wherein the means for modifying the height of theloops includes means for automatically developing a signal soproportioned to said error signal as to compensate for non-linearitiesin the relationship between mass flow of the product and the productfill dimension.
 6. Apparatus for automatic control of the fill dimensionof a product formed in a rolling mill, said apparatus comprising: a. aplurality of stands for performing a work function on the product; b.means for forming a loop in the product between successive stands, eachloop having a height within a predetermined range; c. sensing means forsensing the fill dimension of the product after completion of the workfunction on the product; d. comparator means for comparing the filldimension with a predetermined reference value to form a resulting errorsignal; and e. means for receiving said error signal and transmitting anoutput signal to effect a change in the height of said loops dependentupon said error signal; f. said last-named means including means formodifying said output signal to increase the magnitude thereof when saidsensing means indicates two successive fill errors in the same directionand to decrease the magnitude thereof when said sensing means indicatessuccessive fill errors in opposite directions.
 7. Apparatus as recitedin claim 6 wherein said means for receiving said error signal includesmeans for multiplying said error signal by a variable gain, and whereinsaid gain is increased when said sensing means indicates two successivefill errors in the same direction and said gain is decreased when saidsensing means indicates successive fill errors in opposite directions.